For normal operation, the Lamp Test pin and BI/RBO (OUT) must be pulled high (connected to the positive supply).
All segments are extinguished when a low (logical zero) signal is applied to pin 4 (OUT). A PWM (pulse-width modulated) signal can be applied to this pin to provided varying brightnesses to the LED display being driven, allowing user control of LED dimming for applications such as power saving by decreasing the brightness during times of low ambient light.